Web Application Firewall

Digital technologies are ruling and renovating the business world of today. Most of the emerging companies are adopting the Internet of things (IOT) and shifting their data to the cloud environment. The growing number of opportunities definitely brings an equal number of challenges too.

One of the greatest challenges the IT world is facing today is tackling security threats. The hackers have effortlessly attacked networks and exploited system-level vulnerability triggering the need for products like firewall and other threat detection systems.

A WAF or Web application firewall greatly assists to safeguard the web applications by separating and monitoring HTTP traffic between a web application and the Internet. WAF stays in front of a web application, scrutinize application activities and block traffic that is harmful or does not comply with certain pre-defined rules.

WAF shields the web applications from assailing such as cross-site forgery, cross-site-scripting, SQL Injection and much more. This type of shielding does not require the modification of the application source code. To summarize, WAF applications act as a mediator between the web applications and the user browsing the website and protect against the attacks targeting the application vulnerability.

web application firewall

Web Application Firewall Architecture

WAF simply intercepts and filters malicious requests before they work to create any sort of damages. A WAF has a large number of architecture and operating mechanisms.

Reverse Proxy: A proxy server normally protects a server from exposure with the use of an intermediary service. A WAF acts as a reverse proxy and guards the server against exposure to threats by pushing the clients to pass through WAF before reaching the server. In this mode, a WAF includes an IP address. Incoming requests to the web applications are directed to WAF which in turn sends a request to the web server. A WAF decrypts and analyzes all incoming requests. In this process, a WAF gains full control of the incoming traffic and filters, rewrite the contents based on the security mechanisms.

Layer 2 Bridge: In this process, a WAF stays in-line and plays the role of a layer 2 switch. Here the WAF monitors the incoming requests and performs passive SSL decryption. WAF blocks the traffic by just leaving behind offending packets. This method provides higher performance than the reverse proxy. But it does not support rewriting contents based on security policy.

Out-of-band: In this method, a WAF is not in-line. The network includes a monitoring port that supplies a copy of the incoming traffic to WAF. Here, a WAF only passively decrypts SSL traffic and can only transfer TCP reset packets to block traffic. This method has a minimum impact on the application and the network. Here a WAF is configured only to detect malicious traffic. This prevents the problem of interrupting false-positive traffic leading to an application outage.

Server Resident: A WAF installed on the host executing the web server is called a server resident. It can either be installed as an independent application or a web server plugin. A WAF installed on a server is not as functional as the other operating modes. They create an extra load on the server and so it is important to check beforehand the server utilization resources prior to WAF installation.

Internet Hosted/Cloud: A most popular option to install WAF is to include a cloud provider to implement a WAF. This works similar to the reverse proxy method. Here a DNS is configured to a point to the cloud. This creates a separate connection to the web application. Since the implementation of a WAF is not under the corporate control, care needs to be taken to ensure compliance requirements are met by the service provider.

Now let us move to some of the commonly used WAFs.


 Web Application Firewall AWS:

A WAF AWS is a web application firewall and assists to safeguard any web application from common web threats that could possibly cause damage to the application, hamper security features or consume the bulk of the resources. AWS WAF provides control and lets the owner decide to block or allow any specific kind of traffic based on predefined security rules.

AWS WAF can also be used to create specific rules that block certain patterns specific to the application. New rules can also be incorporated very soon and this also helps the owner to react swiftly to changing traffic patterns. For Example, web requests can be filtered based on IP addresses, HTTP headers, HTTP body or URI strings.

AWS also provides a full-featured API that assists to automate the formation, deployment and maintenance of web security rules. Each and every feature can be configured by employing this API or AWS Management Console. Such configurations permit the creation of application specific rules that enhance web security at the time of the deployment. It permits the formation of web security rules at each and every stage right from the coding phase to the software deployment and even at the audit phase.

AWS WAF can also be used simply to monitor requests that match the filter criteria. It provides almost real-time visibility of web traffic. This can be subsequently used to design new rules or alerts in Amazon Cloud Watch. AWS WAF includes a set of Managed rules that provide web protection against commonly occurring threats. Such rules get automatically updated by AWS security providers once new threats or vulnerabilities emerge.

Deployment of AWS WAF can be made very easily either on Amazon Cloud Front as one of the steps of CDN solution or Application Load Balancer (ALB) that faces the web servers or Amazon gateway for APIs.


 Web Application Firewall Azure:

Azure Application Gateway provides a web application firewall that imparts centralized protection to web applications from malicious threats and other bad actors. WAF Azure makes security management a simple process.

WAF azure safeguards the applications from various issues including HTTP protocol variations, HTTP protocol anomalies, HTTP denial of service, SQL injection, Bots, scanners and much more. WAF Azure works by centrally patching a known vulnerability. It prevents the need to secure each individual web application.

The application gateway is based on a core set of rules from OWASP (Open Web Application Security Project). The security enhancements of Application Gateway consist of SSL policy management and end-to-end SSL support. Such security is further strengthened by the integration of WAF Azure into Application Gateway. This not only protects the web applications from possible warnings but also allows an easy-to-configure central position to control.

Application Gateway WAF monitors web applications against threats using a real-time WAF log. This log is integrated with Azure Monitor to track WAF alerts and effortlessly observe trends. The customers gain complete control over these logs and can also include company-specific retention policies. Such logs also can be ingested by the customers into their analytics system.

Application Gateway gets integrated with Azure Security Centre and this center provides a centralized view of the security state of all Azure specific resources. Azure center scrutinizes the applications for threats and also provides a solution for detected issues.

ALSO READ : AWS vs Azure | Amazon vs Microsoft Cloud Comparison

Web Application Firewall Cloudflare:

Cloudflare WAF safeguards the web applications from common threats like SQL injection attacks, cross-site scripting and forgery attacks without modifying the source code. Cloudflare tracks and removes most of the attacks right at the name-server level before they actually hit the server. Cloudflare provides a secure environment for web applications. Cloudflare works both in a static and dynamic environment.

Cloudflare employs the concept of collective intelligence. It monitors several million requests every second and continuously blocks attacks. When a new custom rule is requested by a customer, Cloudflare analyses with million other applications on the network and checks if the rule is applicable to other applications too. If it does, Cloudflare instantly applies the rule to everybody else in the network. Such properties make the Cloudflare WAF stronger and safer too.

Cloudflare is a free CDN and can be integrated easily. It provides a single source of control for the security of web applications and APIs hosted across multiple environments. It swiftly creates rules to prevent emerging and sophisticated attacks.

A rule is based on several request attributes such as user-agent, path, country, IP, etc. Cloudflare attacks and analyzes every single threat and records it. Cloudflare’s network then shields the web applications across all cloud providers.


Web Application Firewall F5:

WAF F5 provides advanced BOT protection, app-layer DDOS protection and also for encrypting crucial data and credentials.

Extended BOT Protection: Behaviour Analytics in WAF F5 has the ability to detect attacks that even patented approaches miss or wrongly block (false positives). WAF F5 can also be used to safeguard against BOTs in mobile apps where JavaScript cannot be used.

The behavior analytics included in WAF F5 supports existing BOT protection against BOTS. It also includes resource exhaustive URL monitoring, CAPTCHA challenges, monitoring transactions between clients and also server latency screening.

Account Takeover: WAF F5 employs app-level encryption making use of its Data Safe solution to safeguard highly sensitive data and credentials. This additional layer can avert standard key loggers and credential capture tools from the browser level.

App-layer Denial of Service (L7 DDoS): WAF F5 monitors normal traffic, creates and implements real-time DDoS Signatures for new app-layer (L7) attacks. The concept of Stress Detection minimizes false positives and makes sure that the mitigation measures occur only when the attack is powerful. WAF F5 also includes features that have the ability to differentiate between gentle and malicious bots, web scrapers and highly impactful hacking attempts.


WAF Security


 Web Application Firewall Open Source

Commercial WAF is always expensive. The following open source Web Application Firewall provides a free solution to protect web applications against most of the malicious threats.

1. Mod Security:

ModSecurity is one of the most frequently used web application firewalls. It works well with Apache Http, Microsoft IIS and Nginx. It tracks all kinds of requests that reach the web server and its respective response from the server against a set of predefined rules. It provides complete protection against Trojan, information leakage, SQL injection, common web attacks and prevents all kinds of newly emerging hacking techniques.

2. Ironbee:

Ironbee is a type of security framework and it is used to build our own WAF. It includes a new application security inspection engine that provides new processing tools for tracking the HTTP traffic. It is highly portable and is designed to work in several deployment modes which include passive, embedded and reverse proxy. The design is also simple and it enables customers to employ their own modules without a deep understanding of the architecture.


Naxsi is appropriate only for Nginx web server and essentially preserves Web applications from cross-site scripting and SQL injection attacks. In NAXSI, only GET and PUT requests are filtered and by default it acts as a drop-by-default firewall. So it is necessary to add the ACCEPT rule for proper execution.

4. Webknight:

Webknight is a WAF that works for Microsoft IIS. It blocks all kinds of bad elements by using an ISAPI filter. It secures the web application by protecting against Buffer overflow, Directory transversal, Character Encoding, Hotlinking and much more. All blocked requests are available in a default configuration and can be easily customized according to the requirement. Webknight also allows the execution of several administrative tasks including statistics.


 Web Application Firewall Gartner:

Gartner is one of the well known global research and advisory firm that provides insights, advice to several leaders in IT, finance marketing and supply chains across the world. Imperva, Cloudflare, F5 Radware Appwall, Symantec WAF, Barracuda WAF are some of the firewalls that have been recognized by the Gartner ’s Magic Quadrant as the pioneers in Web Application Firewall.

They effectively protect the web applications from all kinds of web-based attacks and provide the perfect balance between performance, security effectiveness and cost. Such WAF consists of a bundle of features that render application layer protection, notable DDOS protection and CDN in an easy to deploy and operating methods.



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